Curable compositions

ABSTRACT

FLUID ORGANOPOLYSILOXANES WHICH ARE VULCANIZABLE AT ROOM TEMPERATURE TO SILICONE ELASTOMERS ARE PREPARED BY MIXING A NOVEL CATALYST SUCH AS THE PROPANEDIOXY BIS(ETHYLACETOACETONATE) COMPLEX OF TITANIUM, CROSS-LINKING AGENT SUCH AS METHYLTRIMETHOXYSILANE AND A SILANOL CHAINSTOPPED POLYDIORGANOSILOXANE FLUID IN THE ABSENCE OF MOISTURE. THESE COMPOSITIONS ARE STABLE, FREE-FLOWING FLUIDS N THE ABSENCE OF MOISTURE BUT CURE TO THE RUBBERY SOLID ELASTIC STATE UPON EXPOSURE TO MOISTURE. THE COMPOSITIONS ARE PARTICULARLY USEFUL AS ADHESIVES AND SEALANTS IN THE CONSTRUCTION OF ELECTRONIC EQUIPMENT IN THAT THEY DO NOT GIVE OFF CORROSIVE BY-PRODUCTS WHEN CURING.

United Patent 3,689,454 Patented Sept. 5, 1972 3,689,454 CURABLECOMPOSITIONS Stanley D. Smith, Ballston Lake, and Stephen B. Hamilton,In, Schenectady, N.Y., assignors to General Electric Company, Waterford,N.Y. No Drawing. Filed Jan. 6, 1971, Ser. No. 104,488 Int. Cl. C08f11/04 US. Cl. 260-465 G 20 Claims ABSTRACT on THE DISCLOSURE Fluidorganopolysiloxanes which are vulcanizable at room temperature tosilicone elastomers are prepared by mixing a novel catalyst such as thepropanedioxy bis(ethylacetoacetonate) complex of titanium, acrosslinking agent such as methyltrimethoxysilane and a silanolchainstopped polydiorganosiloxane fluid in the absence of moisture.These compositions are stable, free-flowing fluids in the absence ofmoisture but cure to the rubbery solid elastic state upon exposure tomoisture. The compositions are particularly useful as adhesives andsealants in the construction of electronic equipment in that they do notgive off corrosive lay-products when curing.

BACKGROUND OF THE INVENTION This invention pertains to fluidorganopolysiloxanes which are capable of vulcanizing at room temperatureto rubbery materials, to the cross-linking, chain extending and chainterminating agents used in such compositions, and to a novel catalystsystem for curing such compositions.

The prior art room temperature vulcanizing materials (RTVs) comprise alinear polymer and a cross-linking agent. The prior art RTVs which havehad commercial success have either given off corrosive by-productsduring cure, have required the mixing of two ingredients immediatelyprior to cure, or have suffered the disadvantage of extreme thickeningduring the initial mixing of the ingredients followed by a viscositydecrease only upon prolonged standing. A disadvantage of the prior artRTVs which gave otf corrosive by-products is that when they were used inconstruction of electronic circuitry the corrosive by-products damagedthe thin copper wires used in the electronic circuits, and any other ofthe electronic components which were corrodable. A disadvantage of theRTVs which had to be mixed immediately prior to cure is that such aprocedure is inconvenient and any of the RTV which is not used, cures toa rubbery state and is unusable. A disadvantage of the RTVs whichthicken immediately upon mixing the ingredients is that it is difficultto handle the material in its thickened state, thus making the mixing,transferring and packaging steps more burdensome.

SUMMARY OF THE INVENTION The RTVs of the present invention comprise asilanol chain-stopped polydiorganosiloxane, at least one silanerepresented by the formula:

and at least one titanium chelate catalyst of the formula:

wherein R is a radical having not more. than about 8 carbon atomsselected from the group consisting of hydrocarbyl, halohydrocarbyl, andcyano lower alkyl, R is a radical having not more than about 8 carbonatoms selected from the group consisting of hydrocarbyl, halohydrocarbyland cyano lower alkyl, R is a radical selected from the group consistingof hydrogen, hydrocarbyl having not more than about 8 carbon atoms,carboxyalkyl and halohydrocarbyl having not more than about 8 carbonatoms and the total number of carbon atoms in the R and R substitutedalkanedioxy radical is not more than about 18, R is a radical having notmore than about 8 carbon atoms selected from the group consisting ofhydrocarbyl, halohydrocarbyl and cyano lower alkyl, R can be selectedfrom the same group as R and in addition can be halo, cyano, nitro,carboxy ester, acyl and bydrocarbyl substituted by halo, cyano, nitro,carboxy ester and acyl, R is selected from the group consisting ofhydrogen, hydrocarbyl having not more than about 8 carbon atoms,halohydrocarbyl having not more than about 8 carbon atoms, acyl havingnot more than about 8 carbon atoms, and taken together with R can formtogether with the carbon atoms to which they are attached cyclichydrocarbon substituents of not more than about 12 carbon atoms andchloro, nitro, acyl, cyano and carboxy ester substituted cyclichydrocarbon substituents; X is a radical selected from the classconsisting of radicals having not more than about 8 carbon atomsselected from the group consisting of hydrocarbyl, halohydrocarbyl,cyanoalkyl, alkoxy, haloalkoxy, cyanoalkoxy and amino, m has a value of0 to 3 and an average value based upon the total amount of silane in thecomposition of 0 to 1.99, 0 has a value of 0 to 8.

The term hydrocarbyl as used here means the hydrocarbon from which onehydrogen atom has been removed, i.e., a monovalent hydrocarbon radical.

The abbreviation of RTV as used herein means a room temperaturevulcanizable material.

In the construction and fabrication of electronic components the mixingimmediately prior to using requirements, the corrosion problems and thethickening and thinning with time problems associated with the prior artRTVs no longer exist. The RTVs of the present invention do not requiremixing immediately prior to use, are stable indefinitely, do not thickenappreciably upon mixing the ingredients, and do not result in corrosionwhen used in electronic circuits.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the formula of thecross-linking agent used in the practice of the present invention R andR can be, for example, mononuclear aryl, such as phenyl, benzyl, tolyl,xylyl and ethylphenyl; halogen-substituted mononuclear aryl, such as2,6-di-chlorophenyl, 4- bromophenyl, 2,5-di-fluorophenyl, 2,4,6trichlorophenyl and 2,5 dibromophenyl; alkyl such as methyl, ethyl,npropyl, isopropyl, n-butyl, sec-butyl, isobutyl, tertbutyl, amyl,hexyl, heptyl, octyl; alkenyl such as vinyl, allyl, nbutenyl-l,n-butenyl-l, n-pentenyl-Z, n-hexenyl-2, 2,3-dimethylbutenyl-Z,n-heptenyl; alkynyl such as propargyl, 2- butynyl; haloalkyl such aschloromethyl, iodomethyl, bromomethyl, fluoromethyl, chloroethyl,iodoethyl, bromoethyl, fluoroethyl, trichloromethyl, di-iodoethyl,tribromomethyl, trifiuoromethyl, dichloroethyl, chloronpropyl,bromo-n-propyl, iodoisopropyl, bromo-n-butyl, bromo-tert-butyl,1,3,3-trichlorobutyl, 1,3,3 tribromobutyl, chloropentyl, bromopentyl,2,3-dichloropentyl,'3,3- dibromopentyl, chlorohexyl, bromohexyl, 1,4dichlorohexyl, 1,3-dibromohexyl, bromooctyl; haloalkenyl such aschlorovinyl, bromovinyl, chloroallyl, bromoallyl, 3-chloron-butenyl-l,3-ch1oro-n-pentenyl-l, 3-fluoro-n-heptenyl-l,1,3,3-trichloro-n-heptenyl-5, 1,3,5 tri-chloro-n-octenyl-6, 2,3,3trichloromethylpentenyl 4; haloalkynyl such as chloropropargyl,bromopropargyl; cycloalkyl, cycloalkenyl and alkyl and halogensubstituted cycloalkyl and cycloalkenyl such as cyclopentyl, cyclohexyl,cycloheptyl, cyclooctyl, 6-methylcyclohexyl, 3,4 dichlorocylohexyl,2,6-dibromocycloheptyl, l-cyclopentenyl, 3 methyl 1 cyclopentenyl, 3,4-dimethyl 1 cyclopentenyl, 5 methyl-5- cyclopentenyl, 3,4 dichloro Scyclopentenyl, 5 (tertbuty1)1 cyclopentenyl, 1 cyclohexenyl, 3 methyl 1-cyclohexenyl, 3,4 dimethyl 1 cyclohexenyl; and cyano lower alkyl such ascyanomethyl, beta-cyanoethyl, gammacyanopropyl, delta-cyanobutyl, andgamma-cyanoisobutyl.

In the formula of the catalyst and in the practice of the presentinvention 2 R can be hydrocarbyl and halohydrocarbyl such as thoselisted above for R or hydrogen. In addition, R can be a 'carboxy alkylof the formula R CO where R is selected from the same group as R and canbe joined to the CO group either through the carbonyl carbon or anoxygen atom of the carboxyl group, R can be hydrocarbyl, halohydrocarbyland cyano alkyl such as those listed above for R, R is a radical havingnot more than about 8 carbon atoms and can be selected from the samegroup as R and in addition can be halo, cyano, nitro, carboxy ester,acyl and substituted hydrocarbyl containing halo, cyano, nitro, carboxyester and acyl, the substituted hydrocarbyl can be derived from thoselisted above for R and the hydrocarbyl portion of the carboxy ester andthe acyl can also be selected from the hydrocarbyl listed above for R, Ris selected from the group consisting of hydrogen, hydrocarbyl havingnot more than about 8 carbon atoms selected from the group set forth inthe definition of R, halohydrocarbyl having not more than about 8 carbonatoms selected from the group set forth in the definition of R, acylhaving not more than about 8 carbon atoms, the hydrocarbyl portion ofwhich is selected from the group set forth in the definition of R. Inaddition, R when taken together with R can form together With the carbonatoms to which they are attached cyclohydrocarbon substituents of notmore than about 12 carbon atoms and chloro, nitro, acyl, cyano andcarboxy ester substituted cyclohydrocarbon substituents, the hydrocarbylportion of the carboxy ester and acyl can be selected from thehydrocarbyl listed above for R, X can be hydrocarbyl, halohydrocarbyland cyanoalkyl such as those listed above for R. In addition, X can be aradical having not more than 8 carbon atoms selected from the groupconsisting of alkoxy, haloalkoxy, and cyanoalkoxy and amine. The groupsrepresented by X can be methoxy, ethoxy, butoxy, propoxy, pentoxy,heptoxy; haloalkoxy such as chloromethoxy, iodomethoxy, bromomethoxy,fluoromethoxy, chloroethoxy, iodoethoxy, bromoethoxy, fluoroethoxy,trichloromethoxy, diiodoethoxy, dibromomethoxy, trifluoromethoxy,dichloroethoxy, chloro n propoxy, bromo n propoxy, iodoisopropoxy, bromon butoxy, bromo tert butoxy, 1,3,3 trichlorobutoxy, 1,3,3tribromobutoxy, chloropentoxy, bromopentoxy, 2,3 dichloropentoxy, 3,3dibromopentoxy, chlorohexoxy, bromohexoxy, 2,4 dichlorohexoxy, 1,3dibromophexoxy, 1,3,4- trichlorohexoxy, chlorohexoxy, chloroheptoxy,bromoheptoxy, fluoroheptoxy, 1,3 dichloroheptoxy, 1,4,4trichloroheptoxy, 2,4 dichloromethylheptoxy, chlorooctoxy, bromooctoxy,iodooctoxy, 2,4 dichloromethylhexoxy, 2,4 dichlorooctoxy, 2,4,4trichloromethylpentoxy, 1,3,5 tribromooctoxy; the cyanoalkoxy can becyanomethoxy, beta-cyanoethoxy, gamma-cyanopropoxy,

delta-cyanobutoxy, gamma-cyanoisobutoxy, beta-cyanopropoxy and alphacyanobutoxy; the hydrocarbyl portions of the amino can be selected fromthe group defined by R and the amino can be, for example, diethylamino,methylamino, diisopropylamino, octylamino, and ethylbutylamino.

The silanol chain-stopped polydiorganosiloxanes useful in the RTVcompositions of this invention can be represented by the formula,

wherein R and R are each organic radicals of not more than 8 carbonatoms selected from the group consisting of hydrocarbyl, halohydrocarbyland cyano lower alkyl, and n is a number from about 10 to about 15,000or more.

The silanol chain-stopped polydiorganosiloxanes are well known in theart and include compositions containing different R and R groups. Forexample, the R groups can be methyl, while the R groups can be phenyland/ or beta-cyanoethyl. Furthermore, within the scope of the definitionof polydiorganosiloxanes useful in this invention are copolymers ofvarious types of diorganosiloxane units, such as silanol chain-stoppedcopolymers of dimethylsiloxane units, diphenylsiloxane units andmethylphenylsiloxane units or, for example, copolymers ofdimethylsiloxane units, methylphenylsiloxane units andmethylvinylsiloxane units. Preferably, at least 50% of the R and Rgroups of the silanol chain-stopped polydiorganosiloxanes are methylgroups.

In Formula 3, the hydrocarbyl, halohydrocarbyl and cyano lower alkylradicals represented by R and R can be selected from the same group asthose listed above for R and R A mixture of various silanolchain-stopped polydiorganosiloxanes also may be employed. The silanolchainstopped materials useful in the RTV compositions of this inventionhave been described as polydior-ganosiloxanes but such materials canalso contain minor amounts, e.g., up to about 20% of monoorganosiloxaneunits such as monoalkylsiloxane units, e.g., monomethylsiloxane unitsand monophenylsiloxane units. The technology involved in incorporatingmonoalkylsiloxane units into RTV compositions is disclosed in US. Pat.3,382,205 of Beers (1968), which is hereby incorporated into the presentapplication by reference. The silanol chain-stopped materials may alsocontain triorganosiloxane units, such as trialkylsiloxane units, e.g.,trimethylsiloxane units, tributylsiloxane units and triphenylsiloxaneunits. The silanol chain-stopped materials may also containt-alkoxysiloxane units, e.g., t-butoxysiloxane units, t-pentoxysiloxaneunits, and t-amyloxysiloxane units. Etfective results can be obtained ifsufiicient t-alkoxysiloxane is utilized in combination with thesilanol-terminated polydiorganosilox-ane of Formula 3 to provide apolymer having a ratio of t-alkoxysiloxane units to silanol of 0.05 to0.9 and preferably 0.2 to 0.8 tert-alkoxydialkylsiloxy units persilanol. Many of the t-alkoxysiloxanes useful as part of the silanolchainstopped materials are described and claimed in 11.8. Pat. 3,438,930of Beers, which issued Apr. 15, 1969 and is assigned to the GeneralElectric Company, the disclosure of which is expressly incorporatedherein by reference.

The silanol chain-stopped polydiorganosiloxanes employed in the practiceof the present invention may vary from low viscosity thin fluids toviscous gums, depending upon the value of n and the nature of theparticular organic groups represented by R and R Examples of silanesuseful in the RTV compositions of this invention include the following:

@suoonm Examples of titanium chelate catalysts of Formula 2 useful inthe RW compositions of this invention include the following:

CH CZ Other examples are readily apparent from the description of thesubstituents which may be present on the titanium.

The alkanedioxy titanium chelates of the present invention can beprepared first by adding a beta-dicarbonyl compound such as abeta-diketone or a beta-ketoester to a titanium ortho ester of a loweraliphatic alcohol. This reaction is represented by the followingequation:

Preferably, two moles of the beta-dicarbonyl compound are used per moleof titanium compound. Toluene is the preferred solvent, preferably inthe amount of from .5 parts to 10 parts per part of alkyl titanate. Inthe above formula R is a lower alkyl radical having 1 to 8 carbon atomsand R R and X are as previously defined. It is preferred thatstoichiometric quantities of reactants be employed as this avoids theproblem of removing um'eactive starting material.

The second step of the preparation involves the reaction of the dialkoxytitanium chelate preparation of which is described above with analkanediol. This reaction is illustrated by the following equation:

In the above formulas, R and R are as previously defined. Again, it ispreferred that the quantities of reactants be stoichiometric. If anexcess of the alkanediol is employed only one of the hydroxyl groups ofsome of the diol will react with the titanium by alkoxy interchange toform hydroxyalkoxy-substituted titanates. In addition to the desiredproduct, the alkoxy'exchange reaction employing the diol also can leadto the formation of minor amounts of polymeric materials where onehydroxy of the diol will react with one titanium chelate and the secondhydroxy will react with the second titanium chelate to form a dimer.Trimer and tetramer formation can also occur in this manner. The use oflarge quantities of solvent such as from two to twenty parts of tolueneper part of the chelated dialkyl titanates tends to diminish trimer andtetramer formation.

It is preferred that when the dicarbonyl compound is a lower alkyl esterof acetoacetic acid that the temperature be maintained below 70 C. Thepreferred dicarbonyl compound is a lower alkyl ester of acetoaceticacid. The alkyl group can be straight chain or branched. The preferredgroup of acetoacetates include methylacetoacetate, ethylacetoacetate,propylacetoacetate, isobutylacetoacetate, pentylacetoacetate,hexylacetoacetate, heptylacetoacetate, and octylacetoacetate. Thepreferred acetoacetate is ethyl acetoacetate. It is also preferred thatR be an isopropyl radical as this via alkoxy interchange j producesisopropyl alcohol. The isopropyl alcohol can then be azeotroped offusing toluene as the azeotroping agent in both of the above-describedreactions.

The use of a solvent is not necessary but is preferred. Solvents otherthan toluene which can be employed include benzene, xylene, hexane orany other of the well known solvents useful for the azeotropic removalof formed alcohol from solution.

.The RTV compositions of the present invention are prepared by simplyadmixing one or more of the silanes of Formula 1, having an average ofat least about 2.01 silicon-bonded alkoxy radicals per silicon atom andthe titanium chelate of Formula 2 with the silanol chainstoppedpolydiorganosiloxane. The components are preferably at room temperatureduring mixing. Since the silanes tend to hydrolyze upon contact withmoisture, care should be exercised to exclude moisture during theaddition of the silane to the silanol chain-stoppedpolydiorganosiloxane. Likewise, care should be taken that the mixture ofthe silane, the titanium chelate and the silanol chain-stoppedpolydiorganosiloxane is maintained under substantially anhydrousconditions if it is desired to store the admixture for an extendedperiod of time prior to conversion of the composition to the cured,solid, elastic silicone rubber state. On the other hand, if it isdesired to permit the mixture to cure immediately upon admixture of thesilane, the titanium chelate and the polydiorganosiloxane, no specialprecautions are necessary and the three components can be mixed andplaced in the form or shape in which it is desired for the compositionto be cured.

The amount of the silane admixed with the silanol chain-stoppedpolydiorganosiloxane can vary within wide limits. However, for bestresults, it isspreferred to add an excess of one mole of the silane permole of silanol groups in the silanol chain-stoppedpolydiorganosiloxanes. Satisfactory curing can be obtained, for example,with from 1.0 to 10 moles of the silane per mole of silanol groups inthe polydiorganosiloxane. No particular detriment is suffered from usingmore than 10 moles of the silane per mole of the polydiorganosiloxaneexcept for a more resinous product being formed-and slowing down thecure. The temperature at which thesilane and the silanol chain=stoppedpolydiorganosiloxane are admixed is not critical and a room temperatureaddition is usually employed.

The admixture can be carried out in the presence of an inert solvent(that is a solvent which will not react with the silanol or alkoxygroups onthe silicon). Suitable solvents include hydrocarbon such' asbenzene, toluene, xylene, orpetroleum ethers; halogenated solvents suchas perchloroethylene or chlorobenzene and organic ethers such asdiethylether and dibutylether; ketones such as methylisobutylketone andfluid hydroxyl-free polysiloxanes. The presence of a solvent isparticularly advantageous when the silanolchain-stopped'polydiorganosiloxane is a high molecular weight gum.The'solvent reduces the overall viscosity ofthe composition andfacilitates cure. The RTV compositions may be kept'in the solvent untilthey are to be used. This is particularly valuable when a gummycompositions is to be employed in coating applications. I

The RTV compositions of this invention are stable in the absence ofmoisture. Consequently, they can be stored for prolonged periods oftimewithout deleterious effect. During this period of storage nosignificant change occurs in the physical properties of the RTVcompositions. This is of particular importance from a commercialstandpoint, since it assures that once an RTV composition is preparedwith a certain consistency and cure time that neither will changesignificantly upon storage. Storage stability is one of thecharacteristicswhich makes the compositions of this inventionparticularly valuable as a one component room temperature vulcanizingcomposition.

A wide choice of components is available in the preparation of the RTVcompositions of the present invention. In general, the particularcomponents employed are a function of the properties desired in thecured silicone rubber. Thus, with a particular silane, some variation inthe properties of the cured silicone rubber are obtained by varying themolecular weight (as measured by viscosity) of the silanol chain-stoppedpolydiorganosiloxane. For a given system, as the viscosity of thesilanol chain-stopped starting material increases, the elongation of thecured rubber increases. On the other hand, with a lower viscositymaterial, the cure is tighter so thatthe cured rubber has a lowerelongation and increased hardness.

RTV compositions prepared by mixing the novel titanium catalyst and thesilane with the silanol chain-stopped polydiorganosiloxanes can be usedwithout further modification in many sealing, caulking or coatingapplications by merely placing the compositions in the desired place andpermitting them to cure upon exposure to the moisture present in theatmosphere. Upon exposure of such compositions to atmospheric moisture,even after storage for times as long as two years or more, a skin willform on the compositions shortly after exposure and cure to the rubberystate will occur within one to three days, all at room temperature. Thetime required for the formation of such skin can vary from a minimum ofabout one hour to a maximum of about eight hours.

It is often desirable to modify the RTV compositions of the presentinvention by the addition of various materials which act as extenders orwhich change various properties such as cure rate and color. Forexample, if it is desired to reduce the time required for complete cure,the composition can be modified by the incorporation of a minor amountof carboxylic acid salt, alkoxide and/or chelate of a metal ranging fromlead to manganese, inclusive, in the electromotive series of metals. Theparticular metals included are lead, tin, nickel, cobalt, iron, cadmium,chromium, zinc and manganese. The carboxylic acids from which the saltsof these metals are derived can be monocarboxylic acids or dicarboxylicacids and the metallic salts can be either soluble or insoluble in thesilanol chainstopped polydiorganosiloxane. Preferably, the saltsemployed are soluble in the silanol chain-stopped polydiorgansiloxanesince this facilitates the uniform dispersion of the salt in thereaction mixture.

Illustrative of metal salts which can be employed are, for example, zincnaphthenate, lead naphthenate, cobalt naphthenate, iron 2-ethy1hexoate,cobalt octoate, zinc octate, lead octoate, chromium octoate and tinoctoate. Operative metal salts include those in which the metallic ioncontains a hydrocarbon substituent such as, for example,carbomethoxyphenyl tin tris-uberate, isobutyl tin triceroate,cyclohexenyl lead triactotinate, xenyl lead trisalicylate, dimethyl tindibutyrate, basic dimethyl tin oleate, triethyl tin tartrate, tributyltin acetate, tri-phenyl tin acetate, dibutyl tin dibenzoate, dibutyl tindioctoate, dibutyl tin maleate, dibutyl tin adipate, diisoamyl tinbistrichlorobenzoate, diphenyl lead diformate, dibutyl tin dilacetate,dicyclopentyl lead bis-monochloroacetate, dibenzyl lead di-2-pentanoate,diallyl lead di-Z-hexenoate, triethyl tin tartrate, tri-butyl tinacetate, tri-phenyl tin acetate, tricyclohexyl tin acrylate, tritolyltin terephthalate tri-n-propyl lead acetate, tristearyl lead succinate,trinaphthyl lead p-methylbenzoate, tris-phenyl lead cyclohexenylacetate, triphenyl lead ethylmalonate, etc.

The amount of the metal salt of the organic carboxylic acid which can beemployed is a function of the increased rate of curing desired so thatany amount of such salt up to the maximum efiective amount forincreasing the cure rate can be employed. In general, no particularbenefit is derived from employing more than about 5% by weight of suchmetal salt based on the weight of the silanol chain-stoppedpolydiorganosiloxane. Preferably, where such metal salt is employed, itis present in an amount equal to from about 0.01% to 2.0% by weight,based on the weight of the polydiorganosiloxane.

Metal chelates such as those disclosed in US. Pats. 3,334,067 and3,065,194 can also be used in the RTV compositions of this invention ascatalysts in amounts from about 0.01 part to about parts based on 100parts of the silanol chain-stopped polydiorganosiloxane.

The alkoxides which can be used in the practice of the present inventioninclude di-butyl tin dimethoxide, dimethyl tin diethoxide, di-butyl tindibutoxide, tin tetraisopropoxide, tin tetramethoxide, and tri-butyl tinmethoxide.

The RTV compositions of the present invention can also be varied by theincorporation of various extenders or fillers. Illustrative of the manyfillers which can be employed with the compositions of the presentinvention are titanium dioxide, lithopone, zinc oxide, zirconiumsilicate, silica aerogel, iron oxide, diatomaceous earth, calciumcarbonate, fumed silica, silazane treated silica, precipitated silica,octamethylcyclotetra siloxane treated silica, glass fibers, magnesiumoxide, chromic oxide, zirconium oxide, aluminum oxide, crushed quartz,calcined clay, asbestos, carbon, graphite, cork, cotton, syntheticfibers, etc. Silazane treated silica fillers such as those disclosed andclaimed in application Ser. No. 789,352 of Smith filed Jan. 6, 1969, nowPat. No. 3,635,743, are particularly suitable for use in the RTVcompositions of the present invention, they are generally employed inamounts from about 5 to about 200 parts filler, per parts of silanolchain-stopped polydiorganosiloxane.

In addition to the modification of the RTV compositions of the presentinvention by addition of metal salt, cure accelerators and fillers,these compositions can also be modified by the incorporation of variousflame retardants, stabilizing agents and plasticizers such as siloxanefluids. Suitable flame retardants include antimony oxide, variouspolyhalogenated hydrocarbons and organic sulfonates.

Where the compositions of the present invention contain components otherthan the silane, the titanium chelate catalyst and thepolydiorganosiloxane, the various ingredients can be added in anydesired order. However, for ease of manufacturing, it is oftenconvenient to form a blend or mixture of all of the components of theroom temperature vulcanizing organopolysiloxane except the silane andthe titanium chelate catalyst, to then remove moisture from theresulting mixture by maintaining the mixture under vacuum and thereafterto add the silane and the titanium chelate catalyst prior to packagingof the composition in containers protected from moisture.

The RTV compositions of the present invention are particularly adaptedfor caulking and sealing applications Where adhesion to various surfacesis important. For example, these materials are useful in householdcaulking applications and industrial applications such as on buildings,factories, automotive equipment and in applications where adhesion tomasonry, glass, plastic, metal and wood is required.

The silanes represented by Formula 1 are well known in the art and aredescribed, for example, in US. Pat. No. 2,843,555 of Berridge.

When the silane is employed as a cross-linking agent, m has a value of 1and the preferred silane is CH Si(OCH When it is desired to have a chainextending agent employed in combination with the cross-linking agent, mhas a value of 2 resulting in the silane being difunctional. Thepreferred difunctional silane is (CH Si(OCH The presence of a chainextending agent results in a final cured product having a higher degreeof elasticity. The same result would be obtained if a higher molecularweight silanol-stopped fluid were used, however, the use of such ahigher molecular weight silanol-stopped fluid would result in a muchhigher viscosity of the curable composition resulting in difficulties inhandling the extremely viscous material.

When it is desired to improve the modulus of elasticity, a silane ofFormula 1, wherein m has a value of 3, is incorporated into the iRTVcomposition. The preferred silane for this application is (CH SiOCH Theuse of this monofunctional silane chain terminating unit in combinationwith the cross-linking and optionally chain extending silanes discussedabove, not only results in a higher modulus of elasticity but in manyinstances also improves the adhesion of the cured compositions to asubstrate.

The preferred silanol chain-stopped polydiorganosiloxanes of Formula 3to be used in combination with the silane cross-linking agent describedabove are silanol chain-stopper polydiorganosiloxanes having a viscosityin the range of about 100 centipoises to 50,000 centipoises at 25 C. Thepreferred polydiorganosiloxanes are polydimethylsiloxanes having fromabout 10 to about 15,000 dimethylsiloxy units per molecule and cancontain some trimethylsiloxy groups. The presence of tertiary alkoxygroups such as t-butoxy groups also improves the adhesion of the RTVs ofthe present invention to particular substrates.

Generally speaking, in the preferred embodiment of the presentinvention, R is an alkyl radical of not more than 4 carbon atoms, R isan alkyl radical of not more than 4 carbon atoms, R is hydrogen, R is analkyl radical of not more than 4 carbon atoms, at least 50% of thegroups represented by R and R are methyl radicals, the remainder phenyl;and n is a number from to 15,000.

The preferred silanes used in the RTV compositions described in thepresent invention contain on the average of from 1.05 to 3silicon-bonded alkoxy groups per silane when a fluid containing twosilanol-containing terminal groups is employed. If the number of alkoxygroups were to be two this would merely result in a build-up of chainlength. Average in this situation means the total number ofsilicon-bonded alkoxy groups divided by the total number of silanemolecules used in the RTV composition. The number, of course, can dropbelow two when the silanolstopped polydiorganosiloxane contains morethan two silanol groups per molecule. This occurs when there is chainbranching in the polydiorganosiloxane and no chain stopping withnonreactive groups such as t-butoxy groups, alkyl groups ortrimethylsilyl groups.

The preferred RTV compositions of the present invention include a tincatalyst such as dibutyl tin dimethoxide.

The preferred RTV compositions of the present invention also includefillers. The most preferred of which is the silazane treated silicafiller disclosed and claimed in application Ser. No. 789,352 of Smith,filed Jan. 6, 1969, now Pat. No. 3,635,743. The fillers are preferablyused in amounts from about 10 to about 100 parts of filler, per 100parts of the silanol chain-stopped polydiorganosiloxane.

The silazane treated filler can be prepared by the following procedure.A fumed silica filler is contacted with ammonia for about 1 /2 hours at25 C. with agitation. Hexamethyldisilazane is added to the treatedfiller in an amount of about 20 parts per 100 parts of treated fillerand the mixture is heated to about 130 C. for about 2 hours. Water in anamount of about one part by weight is added to the mixture and heatingis continued at 130 C. for an additional hour. The treated silica filleris then purged with N at 130 C. until the NH content is 50 p.p.m.

EXAMPLE 1 Ethylacetolacetate (268 parts) was added to 294 parts oftetraisopropyltitanate with stirring over a period of 2 hours. Stirringof this slightly exothermic reaction for an additional 2 hours wasfollowed by removal of the formed isopropyl alcohol by distillation. Arapid addition of 78.5 parts of 1,3-propanediol to the resultingdiisopropyltitanium bis(ethylacetoacetate) was carried out, and thenthis reaction mixture was allowed to stir at ambient temperature for 3hours. Next a slow distillation was carried out using temperatures of 61to 68 C., a heated Vigreaux column and a slight vacuum to remove theformed isopropyl alcohol and to shift the equilibrium in favor of thedesired product. Toward the end of the distillation, 80 parts ofanhydrous benzene was added to azeotrope off residual amounts ofisopropyl alcohol and finally high vacuum stripping was employed. Theresulting product (388 parts) was a yellowish, orange non-transparentviscous liquid at room temperature and a nonviscous liquid at 67 C.Infrared and nuclear magnetic resonance spectra were consistent with theproposed struc ture. The product was found to have a molecular weight of437, the elemental analysis showed carbon 47.6%, hydrogen 6.6%, andtitanium 12.4% as opposed to a theoretical carbon of 47.4%, hydrogen6.3% and titanium 12.60%. The product has the formula One hundred partsby weight of a mixture, containing 100 parts of a 10,000 centipoisehydroxy endblocked dimethylpolysiloxane fluid, 15 parts oftrimethylsiloxane terminated polydimethylsiloxane fluid and 20 parts ofoctamethylcyclotetrasiloxane treated fumed silica was mixed with 5.1parts of methyltrimethoxysilane, 0.93 parts of 1,3-propanedioxytitaniumbis(ethylacetoacetate) of the formula shown above, and 1.0 parts ofacetonitrile. The resulting RTV composition had a constant tack freetime of 3 /2 hours and showed no change in viscosity or cure rate withaging. Cured sheets of this RTV composition were found to have a tensileof 380 p.s.i., an elongation of 350% and a durometer of 27. Extensivestudies of the above RTV composition and of similar RTV compositionscontaining 1,3-propanedioxytitanium bis(ethylacetoacetate) havedisclosed that such systems cause absolutely no corrosion to brass.

EXAMPLE 2 The 1,3-propanedioxytitanium bis(acetylacetonate) was preparedby the following procedure. To 350 parts of tetraisopropyltitanate wasadded 246 parts of acetylacetone with stirring over a period of twohours. Stirring of this slightly exothermic reaction mixture for 16hours at ambient temperatures was followed by removal of the formedisopropyl alcohol by distillation under reduced pressure. A rapidaddition of 94 parts of 1,3- propanediol was carried out, and then, themixture was stirred at 6887 C. for two hours. A slow distillation wascarried out using a slight vacuum, a heated Vigreaux column andtemperatures of 75-84 C. to remove the formed isopropyl alcohol and toshift the equilibrium in favor of the desired product. Finally, a highvacuum stripping was employed to remove residual amounts of isopropylalcohol and excess reactants. A nearly quantitative yield of the darkreddish, viscous product (382 parts) was obtained. Infrared and nuclearmagnetic resonance spectra of the product were consistent with theproposed structure and vapor phase osmometry measurements disclosed thatthe product had a molecular weight of 410.

One hundred parts by weight of a 10,000 centipoise hydroxyl endblockedpolydimethylsiloxane fluid was mixed with 15 parts of trimethylsiloxaneendblocked polydimethylsiloxane fluid as a plasticizer, and 20 parts ofoctamethylcyclotetrasiloxane treated finely divided fumed silica. 100parts of this base was then mixed with 4.2 parts ofmethyltrimethoxysilane, 1.0 parts of the 1,3- propanedioxytitaniumbis(acetylacetonate) dissolved in 1.6 parts of acetonitrile. Theresulting RTV composition has a fairly constant tack free time of 2hours, had a good through cure after several days of exposure toatmospheric moisture and showed no change in cure rate or viscosityafter accelerated aging at 50 C. for one month. Cured sheets of theabove-described RTV composition were found to have a tensile strength of300 p.s.i., an elongation of 400% and a durometer of 27. In addition,the above material was found to have an unprimed peel adhesion of 21lbs/in. from alclad aluminum with adhesive failure. This RTV system wasfound to cause slight corrosion to brass when tested in accordance withconventional military specifications.

EXAMPLES 3 AND 4 A series of comparative studies in which four differentRTV compositions, differing only in the titanium chelate catalyst, hasbeen carried out. A base mixture, which consisted of parts of 10,000centipoise hydroxy endblocked dimethylpolysiloxane fluid, 15 parts oftrimethylsiloxy terminated polydimethylsiloxane fluid and 20 parts ofoctamethylcyclotetrasiloxane fumed silica was used for each RTVcomposition. The RTV compositions in each case were comprised of 100parts of the abovedescribed base compound, 4 parts ofmethyltrimethoxysilane, 1.02 parts of acetonitrile and 1.74 mmole per100 grams of base compound of one of the following titanium chelates:1,3 propanedioxytitanium bis(ethylacetate) (II), 1,3propanedioxytitanium bis(acetylaceacetate)(II), 1,3-propanedioxytitanium bis(acetylacetonate) (III) and diisopropoxytitaniumbis(acetylacetonate) (IV). The factors determined for each RTVcomposition were cure rate, application rate and viscosity all as afunction of time from immediately after catalyzation up to four weeks.Also, the physical properties of cured sheets were measured for each RTVcomposition. The findings of this comparative study are summarized inTables I and II, whereby the properties of the different RTVcompositions are shown.

When a hydroxy terminated polysiloxane, methyltrimethoxysilane and adialkoxytitanium chelate or an al- =kanedioxytitanium chelate are mixedto form an RTV composition, the mixture increases in viscosity to reacha maximum and then decreases in viscosity (increases in applicationrate) with time until a final state is reached. Of the RTV systemsstudied, this very undesirable eifect of structuring during and aftercatalyzation was found to be significantly smaller with the1,3-propanedioxytitanium chelates (I, III) Also, the rate at which theRTV composition passed through this structured state or maximumviscosity was much greater with the alkanedioxytitanium chelates (I andIII). The viscosities immediately after catalyzation and after the RTVhas reached a final state were less with the 1,3-propanedioxytitaniumchelates (I, III) than the corresponding viscosities of the RTV systemswith the diisopropoxytitanium chelates (II, IV). An additionalsignificant difference is seen in a comparison of the tensile strengthsof elastomers prepared using the 1,3- propanedioxy chelates (I, III) andthe isopropoxytitanium chelates (II, IV). The materials preparedaccording to the teachings of the present invention have tensilestrengths approximately double those comparatively tested. In addition,as shown in Table 1, the application rates of RTVs made using chelates Iand III are many times greater than chelates II and IV. This increase inapplication rate is of considerable practical significance since itrepresents the maximum rate at which the RTV can be applied from aconventional container under standard conditions.

TABLE I Application rate Viscosity b (grams/mm.) after time of (1X10cps.) after time of- Titanium chelate 0 hrs. 24 hrs. 48 hrs. 1 wk. 4wks. 0 hrs. 24 hrs. 48 hrs. 1 wk. 4 wks.

(III) 10. 3 186 138 23 3. 2 1. 7 1. 8 1. 7

li- PILO l T1.

The application rates were determined using a inch orifice and 90 lbs.of inert gas pressure. b A Brookfield HBF viscometer and No. 7 spindlewere used for all viscosity measurements.

TABLE II Physical Properties of cured sheets Elongation Cure Tensile(percent at Durometer rate, Titanium chelate (lbs/in?) break) (Shore A)hrs.

(I) 427 440 29 1 H 1, 0R;- B T f CH (III) 424 480 29 2% CH n 0 5 Z cCjik /TL CH 2 art 2 TABLE IIContinued Elongation Cure Tensile (percentat Durometer rate, Titanium chelate (lbs./in.'-) break) (Shore A) hrs.

J I Ha (IV) 188 384 30 1% k (who); ,0}:

l Tack tree time after 1 wk. aging.

The diisopropoxytitanium bis(ethylacetoacetate) of Formula II and thediisopropoxytitanium bis(acetoacetate) of Formula IV are knowncompositions of matter. The 1,3-propanedioxytitaniumbis(ethylacetoacetate) was prepared by the procedure set forth inExample 1.

The 1,3-propanedioxytitanium bis(acetoacetate) of Formula III wasprepared by the procedure described in Example 2.

What we claim is:

1. A fluid composition stable under substantially anhydrous conditionsand curable to an elastic solid in the presence of moisture whichcomprises a silanol chainstopped polydiorganosiloxane, represented bythe formula,

lt l.

wherein R and R are a radical having not more than about 8 carbon atomsselected from the class consisting of hydrocarbyl, halohydrocarbyl andcyano lower alkyl wherein the radicals R and R may be different fromeach other and it varies from about to about 15,000, at least one silanerepresented by the formula:

R Si 0R and at least one titanium chelate catalyst of the formula:

wherein R is a radical having not more than about 8 carbon atomsselected from the group consisting of hydrocarbyl, halohydrocarbyl, andcyano lower alkyl, R is a radical having not more than about 8 carbonatoms selected from the group consisting of hydrocarbyl,halohydrocarbyl, and cyano lower alkyl, R is a radical selected from thegroup consisting of hydrogen, hydrocarbyl having not more than about 8carbon atoms, carboxyalkyl and halohydrocarbyl having not more thanabout 8 carbon atoms and the total number of carbon atoms in the R and Rsubstituted alkanedioxy radical is not more than about 18, R is aradical having not more than about 8 carbon atoms selected from thegroup consisting of hydrocarbyl, halohydrocarbyl and cyano lower alkyl,R is selected from the same group as R halo, cyano, nitro, carboxyester, acyl and hydrocarbyl substituted by halo, cyano, nitro, carboxyester and acyl, R is selected from the group consisting of hydrogen,hydrocarbyl having not more than about 8 carbon atoms, halohydrocarbylhaving not more than about 8 carbon atoms, acyl having not more thanabout 8 carbon atoms, and taken together with R forms together with thecarbon atoms to which they are attached cyclichydrocarbon substituentsof not more than about 12 carbon atoms and chloro, nitro, acyl, cyanovalue based upon the total amount of silane in the composition of 0 to1.99, 0 has a value of 0 to 8, and such that when 0 is zero the moietiesare bonded to each other in a cyclic fashion.

2. The composition of claim 1 further characterized by at least 50% ofthe total number of R and R groups being methyl radicals.

3. The composition of claim 2 further characterized by the remaining Rand R groups being phenyl radicals.

4. The composition of claim 1 further characterized by R, R and R beingalkyl radicals and R and R being hydrogen.

5. The composition of claim 1 further characterized by R, R and R beingmethyl radicals, X being OC H and 0 having a value of zero or 1.

6. The composition of claim 5 further characterized by R and R being H.Y

7. The composition of claim 1 further characterized by R, R R and Xbeing methyl radicals and R and R being H.

8. The composition of claim 1 further characterized by the mixtureconsisting of and 1 CH: l no sio n where n is a number from about 10 toabout 15,000.

9. The composition of claim 1 further characterized by the mixtureconsisting of locu 3 and I OH: i HO-SiOH L ICE:

m )4 m and at least one titanium chelate catalyst of the formula:

wherein R is a radical having not more than about 8 carbon atomsselected from the group consisting of hydrocarbyl, halohydrocarbyl, andcyano lower alkyl, R is a radical having not more than about 8 carbonatoms selected from the group consisting of hydrocarbyl, halohydrocarbyland cyano lower alkyl, R is a radical selected from the group consistingof hydrogen, hydrocarbyl having not more than about 8 carbon atoms,carboxyalkyl and halohydrocarbyl having not more than about 8 carbonatoms and the total number of carbon atoms in the R and R substitutedalkanedioxy radical is not more than about 18, R is a radical having notmore than about 8 carbon atoms selected from the group consisting ofhydrocarbyl, halohydrocarbyl and cyano lower alkyl, R is selected fromthe same group as R halo, cyano, nitro, carboxy ester, acyl andhydrocarbyl substituted by halo, cyano, nitro, carboxy ester and acyl, Ris selected from the group consisting of hydrogen, hydrocarbyl havingnot more than about 8 carbon atoms, halohydrocarbyl having not more thanabout 8 carbon atoms, acyl having not more than about 8 carbon atoms,and taken together with R forms together with the carbon atoms to whichthey are attached cyclichydrocarbon substituents of not more than about12 carbon atoms and chloro, nitro, acyl, cyano and carboxy estersubstituted cyclichydrocarbon substituents, X is a radical selected fromthe class consisting of radicals having not more than about 8 carbonatoms selected from the group consisting of hydrocarbyl,halohydrocarbyl, cyanoalkyl, alkoxy, haloalkoxy, cyanoalkoxy and amino,m has a value of 0 to 3 and an average value based upon the total amountof silane in the composition of 0 to 1.99, 0 has a value of 0 to 8, andsuch that when 0 is zero the moieties are bonded to each other in acyclic fashion.

12. The method of claim 4 further characterized by at least 50% of thetotal number of R and R groups being methyl radicals.

18 13. The method of claim 12 further characterized by the remaining Rand R groups being phenyl radicals.

14. The method of claim 11 further characterized by R, R and R beingalkyl radicals and R and R being hydrogen.

15. The method of claim 11 further characterized by R, R and R beingmethyl radicals, X being -OC H and 0 having a value of zero or 1.

16. The method of claim 15 further characterized by R and R being H.

17. The method of claim 11 further characterized by R, R R and X beingmethyl radicals and "R and R being H. i

18. The method of claim 11 further characterized by the mixtureconsisting of 3 CH-0 ,a=t ii 2 Tt cn en,- 0 ac 3 2 and CH3 HO S iO- l(1H3 where n is a number from about 10 to about 15,000.

19. The method of claim 11 further characterized by the mixtureconsisting of w st l0CH l where n is a number from about 10 to about15,000.

20. The method of claim 11 further characterized by 0 being 0 or 1 and Rbeing hydrogen or methyl.

References Cited UNITED STATES PATENTS 3,334,067 8/1967 Weyenberg 260-465 3,499,859 3/ 1970 Matherly 260-37 DONALD E. OZAIA, Primary ExaminerM. I. MARQUIS, Assistant Examiner US. Cl. X. R.

117-123 D, 135.1, 138.8 R, 143 R; 260-185, 32.8 SB, 33.2 SB, 33.6 SB,33.8 SB, 37 SB, 45.7 S, 45.75 R, 46.5 E, 825

